JERUSALEM — Nine Palestinians were killed Wednesday in Israel's continuing offensive in the Gaza Strip, including a boy, 14, who had gathered with friends to watch the fighting.

Since early Sunday, the Israeli Army has been looking for smuggling tunnels and explosives in northern Gaza City, in the Shijaiyeh neighborhood, and 19 Palestinians have been killed.

On Wednesday, the Israelis said they had discovered a tunnel stretching about 150 meters from a house toward the Karni cargo crossing between the Gaza Strip and Israel.

Israel has closed cargo and pedestrian crossing points in Gaza for long stretches this year because of security alerts, and it has been closed since Aug. 16 in the latest round. When the crossing is shut, it is almost impossible for goods to enter or leave Gaza.

The Israelis said the tunnel began in a building nearly a kilometer from the border fence so the digging would not be visible. They speculated that the tunnel was being dug to carry out an attack on the Karni crossing.

The army said in a statement: "The tunnel was intended to be used for a large-scale terror attack, apparently against the crossing itself."

On June 25, Palestinian militants used a long tunnel near Rafah to enter Israel, kill two Israeli soldiers and capture another, Gilad Shalit, who remains in captivity.

Three days later, Israeli forces entered Gaza for the first time since they had withdrawn last August and have been fighting there since then, throughout the army's 34-day invasion of Lebanon.

At least 200 Palestinians have been killed in the Israeli operation.

The United States has proposed bolstering security at Karni by deploying 90 international monitors on the Palestinian side and constructing better facilities there. Israel says it will consider the proposal only after Shalit is freed.

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The U.S. proposal would expand Karni, a key lifeline for Gaza that is usually closed by Israel. The foreign monitors, probably European like those at the Rafah crossing between Gaza and Egypt, would oversee the work of the Palestinians. A U.S. official said that contrary to early reports, no American monitors would be involved.

In the West Bank, the Palestinian president, Mahmoud Abbas, called again on militants to stop firing Qassam and other rockets into Israel. Abbas said that too many Palestinians were dying in Gaza for little reason.

"What is happening in Gaza as a result of rockets fired in vain must stop right now because there is no interest in this continuing," Abbas said.

He spoke to 3,000 civil servants who were protesting the failure of the Hamas- led Palestinian Authority to pay their salaries. A smaller, similar rally took place in Gaza City, with 200 children of civil servants protesting outside the office of Prime Minister Ismail Haniya.

On Tuesday, 300 unemployed Palestinian workers surrounded Parliament and scuffled with the police.

Abbas, who met Wednesday with Secretary General Kofi Annan of the United Nations, will head to Gaza City for conversations with Haniya on the formation of a national-unity government that might persuade Israel and Western nations to lift their freeze on financing the Palestinian Authority. Hamas has rejected demands that it recognize Israel's right to exist, renounce violence and accept previous Israeli- Palestinian agreements.

Yuval Diskin, the head of Israel's Shin Bet security agency, told Parliament that Palestinian militants were smuggling large amounts of weapons, including rockets, through as many as 20 tunnels dug under the Gaza-Egypt border. "Except for tanks and planes, they are smuggling everything," he said, according to legislators quoted in the Israeli media.

The border is supposed to be controlled by Egypt and the Palestinians, with Europeans monitoring the formal crossing terminal at Rafah. But the Europeans are not responsible for patrolling the border.

The West Bank leader of the military wing of Islamic Jihad, Hossam Jaradat, died Wednesday in a hospital in Jordan. Jaradat, 43, was shot Aug. 23 during a raid on the Jenin refugee camp. He was taken to a Jenin hospital but then evacuated to Jordan.